Coated metallic centrifugal pipe mold



Jan. 8, H w STUART ET AL COATED METALLIC CENTRIFUGAL PIPE MOLD FiledMarch 22, 1934 Eeneri Hfiiuarl, q liora/ce 61 Hand far/ml 1;. Haw/old;

A T TOK/VEV -.MQ-UNITED-STATES PATENT oF icE' Patented Jan. 8, i935 r1,986,985 COATED METALLIC CENTRIFUGAL PIPE 1 MOLD' Herbert W. Stuart,Beverly, Horace S. Hunt, Bur-, lington, and Paul L. Arnold, EdgewaterPark,

N.J., assignors to United States Pipe and Foundry Company, Burlington,N. J., a corporation of New Jersey Application March 22. 1934, SerialNo. 716,768

5 Claims. (01. 22 1s9 Our invention relates to the coating of metalthemetal surface of the mold and project in lic centrifugal pipe molds witha finely divided large part through the inner surface of the coatl drycoating material of ,such loosely adherent ing formed by the finelydivided dry coating ma and loosely coherent structure as results fromthe terial. The distribution .of the sand grains to 5 application of theflnelydivided dry coating mabring about the actualecontact of a verylarge 5 terial tothe mold by directinga. jet of a carrier pr p rti n fth rain with the m tallic surgas charged with the. finely divided drycoating face of the mold is'best eilected by charging the materialagainst successive contiguous areas of j of Ca e ga Charged With fi ydivided y the mold surface, that is to say, by the method coatingmaterial with an additional charge of the I described and claimed andillustrated in one sand. like grains which, owing to their greater 10mode of application in, the patent granted to mass, will, as the coatingis applied to the mold Me'ssraR'ussell and Langenber'g, Number 1,949,433be projected through the finely divided material of March 6, 1934. Inthe centrifugal casting of so as to come in large part in contact withthe, pipes in molds coated with the finely divided dry metallic moldsurface while the size of the grains coating material as described inthe said Russell will be such that they will, at the time the molten 15and Langenberg patent, under certain conditions metal comes in contactwith the coating, project with rgard to the fluidity of the molten ironin part beyond the inner surface of the portion poured into the mold,the molten metal will not of the coating formed by the finely divideddry at all times pick up the rotary motion of the mold coating materialand come in actualcontact with with sufllcient promptness to insure thatafter the molten metal.

,. contacting with the coatedmold surface it would By preference we usefor the sand like grains of be carried along by the mold with sufficientspeed our composite coating silica sand, the .particle to insure thatits centrifugal motion will hold size of which, or of any otheravailable sand like it in contact with the mold and, as a result, por-,material, should be such that it will pass a sieve tions of the moltenmetalwill at times fall away of 20 meshes to the inch, more preferably,a sieve, 5 from the surface of the mold carrying with it of meshes,while approximately 75% of the portions of the coating material andfalling upon sand is retained on a sieve of 50, meshes to the the moltenmetal lying at the time beneath the inch. Any other sand like materialhaving a falling metal and from both causes imperfect hard, compact,crystalline structure and substan- 30 pipes are produced characterizedby what are tially nonreactive and nonfusible under condi- 30 known asmold splashes and liable to have undetions existing during the castingof a pipecan sirable areas of chill. The object of our zinvenbe used inplace of silica sand, as, for example, tion is to so change or modifythe structure of carborundum, but pains should be taken that the thecoating applied to the mold that it will at grains of sand like materialare of such structure l the same time be less liable to slip on thesurface as to retain their form without breaking up under 35 of themetallic mold to which it is applied and the stresses to which they aresubjected during more able to take a bettergrip upon the freshly castingand it is also importantthat the sand like poured metal, therebydecreasing the liability ofmaterial should be uncontaminated with clayor the molten metal to slip on'the surface of the other material whichmight act like a lubricant 0- coating or to cause a slipping of thecoating on and prevent the proper adhesion of the sand like 40 thesurface of the mold, thus insuring'that the grains to the mold surfaceor impair their grip rotary motion of the mold shall be more promptlyupon the molten metal. transmitted to the molten metal flowing into thei We have found in practice that the necessary mold. These results can,we have discovered, be percentage of the sand like grains to be admixedeffected by admixing with the fin ly ivided dry with the finely divideddry coating material will 45 coating material formingthe coating of thevary very largely with variations in the fluidity mold, sand like grainsof a hard and. compact, of the molten iron, under certain conditions ancrystalline structure and of a. substance or subadmixture of 5% byvolume of sand with the finestances substantially non-reactive andsubstanly divided dry coating material will be effective.

, tially nonfusible under conditionsexisting durwhile under certainother conditions, omen; ind? 50 ing the casting of a pipe, the sand likegrains befrequent occurrence,,l..iwerahawe"i fuundzrithatiian ing ofmaterially larger size than the particlesadmigetlusmofmirdixofithasaiidelikeog ainsewamadffln ly div d drycoating material ,ang QQ1S' vantagfibjlilfi,shill}ffifllfllbQIfiGlZlEfEkMflTlfiftlOfl3WhiCh tributed through the iingly, dttidfidiigoil ih am naue ia le toro cilrlin-ipractice weihawefiouridihat atililqhetf l tl teeblbe d tc rtw ti hleacia mixturovofiaototZfifiijohthmsandhkqgrains? s5 is adequate and satisfactory andpresents no objectionablefeatures where conditions as to the fluidity ofthe molten metal are such that no admixture of the sand like grains withthe finely divided dry coating material is necessary.

For practical purposes it has been found desirable that the particlesize of the finely'divided -dry coating material should be approximatelysuch that it will passa sieve of approximately 150 meshes to theinch'and it is with material of 'approximately this fineness thatwe-prefer to use the sand like grains having the characteristics whichwe have described and a size .which will pass a sieve of 20 meshes tothe inch while approximately 75% is retained on a sieve of 50 meshes tothe inch.

As pointed out in the Russell and Langenberg patent, it is preferablethat the coating applied to the metallic centrifugal mold should not,for

the best results be-materially thicker than is necessary to effect suchretardation in the cooling of the molten'metal as will avoid theformation of a chill both because with increased thickness in thecoating there is more liability to slips and fractures impairing itscontinuity and'because the character of the casting is better than wherethe retardation in the cooling of the metal is greater. Under someconditions, however, it may be desirable to increase the thickness ofthe coating and'this we have found can be accomplished by the use of ourcompositecoating which is distinctly less liable to fracture underconditions of use than'is thecoating formed of the finely divided Idrycoating material :without the P incorporation'of the sand element.

It is distinctly advantageous that the "finely divided dry coatingmaterial should be'used in such quantity that when evenly and compactlydistributed over the surface of the mold it will form a coating thedepth of which will be less than that of the diameter of a material percentage of the sand-like grains admixed with the finely divided-drycoating material so that such grains even though running in contact withthe surface of the-metal mold will,atthe' time molten "metal is chargedintothe coatedmol'd,-' project inward beyond the surface of thecoating-formedby the finely divided material and'come in actual contactwith the surface of the casting.

The admixture of sand like grains with "the finely divided dry coatingmaterial facilitates the handling of the coating material in the feedingmechanism in that it materially increases what we may call the fluidityof the composite coating material as comparedwith that of the finelydivided dry coating material when usedalone, greatly lessening theliability or the coating material clogging in some part of the feedingmechanism and making the feed-more accurate in any class of feedingapparatus which may beemployed'to deliver the coating material to thecarrier gas jet.

Our invention may'perhaps be better understood as described inconnection with the drawing which forms part of this specification andin which Figure l is an'elevation of a centrifugal pipe casting machineadapted for use inthe practice of our improved method of coating themold and Figure 2 is a somewhat diagrammatic'illustration showing one,greatlyexaggerated scale the general structure of our improved'coatingasapplied to a centrifugal metallic pipe mold.

The apparatus illustrated in Fig. 1 is essentially the same as thatdescribed in the Russell and Langenberg Patent No. 1,949,433. with theexception that in addition to the feeding mechanism indicated at G andoperating to feed the finely divided dry coating material through thehopper'F to the gun F, we have indicated at g a supplementary feedingdevice adapted also to deliver coating material to the hopper F As, in

all other respects, the apparatus indicated is the same as'thatdescribed in the Russell and Langenberg patent, it is unnecessary todescribe it in detail except perhaps to note that the coating materialsfed to the gun F are picked up in'the gun 'by a jet of carrier gasintroduced through the nozzle indicated at F and the so chargedsjet ofcarrier gas transferred through the conduitE'to the nozzle E whichdirects the jet against the inner surface of the rotating mold D inadvance of the contact of the molten metal fed to the mold through thespout C Ordinarily, we have found it to be satisfactory and convenientto charge a single feeding mechanism such as is indicated at G with athoroughly admixed charge of'the finely divided coating material andsand in the proportion, say of 20 to 25% of sand by volume to that ofthe finely divid- :ed dry coating materialas a mixture of this characteris found to give satisfactory results 'in'the character of the coatingapplied to the mold under practically all ordinary conditions of the"molten'metal poured intothe mold but where it is desired to moreexactly regulate the condition of the coating to the conditionofthe-metal, this can be effected by charging onefeeding device,

:such as G, with the 'finely divided dry coating material and anotherfeeding'device, such as g,

withthe sand so thatby regulating the-irate of "feed of the feedingdevice g. any desired percentage of sand can be fed to'the gun, with theconsequent' formation of a coating .in which the sand constituent willmore closely approximate that which is found to be best in view of'thecharac- 'ter of the molten metal which at any timeis being fed'to themold. The construction of .the feeding device indicated atG andrgsispreferably that of United States PatentNo. l ,939',703,granted 'December19, 11933, but :any feeding :device :capable of delivering anicelyregulated supply of mold coating materialmay be used and'while webelieve that apparatus of the kind indicated in Fig. l and fullydescribed in the patent :to :Rus-

sell and Langenberg is that best adapted for use in coating and castingpipes, it must beun'derstood that our invention is in no wise limited tothe use of such an apparatus'but is applicable to any method in which ajet of carrier gas directed-progressively against contiguous areas of'a' metallic centrifugal mold is charged with .finely divided moldcoating material and also with sand grains of the general characterwhich'we haveindicated as usable in connection with our process 1 andadapted in connection with the finelyhdivided material to buildup ournew mold'coating as, for example, the apparatus described .and shown inthe applications filed by Russell and Langenberg on June 6, 1933,SerialNumbers, 674,502;

of the mold A and to project in large part through the surface of thecoating of finely divided dry coating material indicated at B. Thedrawing, it will be understood, is greatly exaggerated and is to beunderstood as in the nature of a diagrammatic showing of the generalstructure of the coating as of the time when the molten metal pouredinto the mold contacts with it.

As is pointed out in the Russell and Langenberg patent, 1,949,433, thecoating of finely divided dry coating material is, at the time of itsapplication to the mold by the jet of carrier gas, permeated by films ofthe carrier gas, the presence of which naturally increases the thicknessof the coating and increases the efficiency of the coating as a retarderof heat transfer. The incorporation of the carrier gas with thefinelydivided dry coating material at the time the coating is applied to themold no doubt facilitates the passage of the sand grains through thefinely divided coating material into contact with the surface of themold but th t at the time of contact of the molten metal ith thecoating, a considerable portion of the sand grains project through thefinely divided coating material and come in contact with the moltenmetal is made evident by the fact that a considerable amount of sandgrains are found adhering to the casting, though very easily brushedaway and not so embedded in the casting as to impair its smoothness.

Having now described our invention, what we claim as new and desire tosecure by Letters Patent, is:

1. An internally coated metallic centrifugal pipe mold characterized inthat its coating is made up of loosely adherent and loosely coherentfinely divided dry particles of mold coating material intermixed withrelatively large sand like called for in claim 1, in which the finelydivided coating material is of such particle fineness as would passthrough a sieve of approximately 150 meshes to the inch and in'which thesand like material is of such particle size that it would pass a sieveof 20 meshes to the inch and preponderantly of such size that it willnot pass a sieve of 50 meshes to the inch.

4. A coated metallic centrifugal pipe mold as called for in claim 1,further characterized in that the sand grains of the composite coatingare so disposed therein as to contact in large part with the surface ofthe metallic mold and to project in large part beyond the surface ofthat portion of the coating formed by the finely divided dry coatingmaterial.

5. A coated metallic centrifugal pipe mold as called for in claim 1,further characterized in that the coating is in part made up of aquantity of the finely divided dry mold coating material which, ifcompactly distributed over the mold surface, would produce a coating ofa thickness less than the diametric size of a substantial percentage ofthe sand grains which are distributed through the finely dividedmaterial.

HERBERT W. STUART. HORACE S. HUNT. PAUL L. ARNOLD.

